Showing papers on "Vanadate published in 2010"

Correlation between Luminescence Quantum Efficiency and Structural Properties of Vanadate Phosphors with Chained, Dimerized, and Isolated VO4 Tetrahedra

Abstract: The internal luminescence quantum efficiency and color properties of AVO3 (A: Li, Na, K, Rb, and Cs), M2V2O7 (M: Mg, Ca, Sr, Ba, and Zn), and M3V2O8 (M: Mg, Ca, Sr, Ba, and Zn) have been investigated. These vanadate phosphors exhibited broadband emission from 400 nm to over 800 nm due to the one-electron charge transfer transition in the VO4 tetrahedra, and the color of the luminescent materials ranged from green to yellow-orange via white, corresponding to 0.277 < x < 0.494 and 0.389 < y < 0.488 on the CIE chromaticity diagram. We found that the luminescence quantum efficiency of the vanadate phosphors with VO4 tetrahedra was strongly enhanced by the strong interaction between V ions and the weak interaction between V and A(M) ions in the crystal structures. We hypothesize that the long exciton diffusion lifetime induced by these structural features enhanced luminescence, leading to high quantum efficiency.

Is vanadate reduced by thiols under biological conditions? Changing the redox potential of V(V)/V(IV) by complexation in aqueous solution.

Abstract: Although dogma states that vanadate is readily reduced by glutathione, cysteine, and other thiols, there are several examples documenting that vanadium(V)−sulfur complexes can form and be observed. This conundrum has impacted life scientists for more than two decades. Investigation of this problem requires an understanding of both the complexes that form from vanadium(IV) and (V) and a representative thiol in aqueous solution. The reactions of vanadate and hydrated vanadyl cation with 2-mercaptoethanol have been investigated using multinuclear NMR, electron paramagnetic resonance (EPR), and UV−vis spectroscopy. Vanadate forms a stable complex of 2:2 stoichiometry with 2-mercaptoethanol at neutral and alkaline pH. In contrast, vanadate can oxidize 2-mercaptoethanol; this process is favored at low pH and high solute concentrations. The complex that forms between aqueous vanadium(IV) and 2-mercaptoethanol has a 1:2 stoichiometry and can be observed at high pH and high 2-mercaptoethanol concentration. The sol...

Energy transfer mechanisms in Yb3+ doped YVO4 near-infrared downconversion phosphor

Abstract: Upon ultraviolet (UV) light excitation, an intense near-infrared (NIR) emission of Yb3+ (F25/2→F27/2) around 980 nm is observed in YVO4:Yb3+ phosphors. Owing to host absorption of YVO4, a broad excitation band ranging from 250 to 350 nm is recorded when the Yb3+ emission was monitored, which suggests an efficient energy transfer from host to Yb3+ ions. The Yb3+ concentration dependence of the visible vanadate emission as well as the Yb3+ emission is investigated. The decay curve of vanadate emission is measured under the excitation of a 266 nm pulsed laser. The decay time of the vanadate emission at 500 nm is remarkably reduced by introducing Yb3+ ions, further verifying that the energy transfer from the vanadate host to the Yb3+ ions is very efficient. Cooperative energy transfer (CET) is discussed as a possible mechanism for the NIR emission. The YVO4:Yb3+ phosphor can convert each UV photon into two NIR photons via CET, which has potential application in the high efficiency silicon-based solar cells.

Development of nanostructured silver vanadates decorated with silver nanoparticles as a novel antibacterial agent

Abstract: In this work we report the synthesis, characterization and application of silver vanadate nanowires decorated with silver nanoparticles as a novel antibacterial agent. These hybrid materials were synthesized by a precipitation reaction of ammonium vanadate and silver nitrate followed by hydrothermal treatment. The silver vanadate nanowires have lengths of the order of microns and diameters around 60 nm. The silver nanoparticles decorating the nanowires present a diameter distribution varying from 1 to 20 nm. The influence of the pH of the reaction medium on the chemical structure and morphology of silver vanadates was studied and we found that synthesis performed at pH 5.5-6.0 led to silver vanadate nanowires with a higher morphological yield. The antimicrobial activity of these materials was evaluated against three strains of Staphylococcus aureus and very promising results were found. The minimum growth inhibiting concentration value against a MRSA strain was found to be ten folds lower than for the antibiotic oxacillin.

Sodium Orthovanadate Inhibits p53-Mediated Apoptosis

Abstract: Sodium orthovanadate (vanadate) inhibits the DNA-binding activity of p53, but its precise effects on p53 function have not been examined. Here, we show that vanadate exerts a potent antiapoptotic activity through both transcription-dependent and transcription-independent mechanisms relative to other p53 inhibitors, including pifithrin (PFT) alpha. We compared the effects of vanadate to PFTalpha and PFTmicro, an inhibitor of transcription-independent apoptosis by p53. Vanadate suppressed p53-associated apoptotic events at the mitochondria, including the loss of mitochondrial membrane potential, the conformational change of Bax and Bak, the mitochondrial translocation of p53, and the interaction of p53 with Bcl-2. Similarly, vanadate suppressed the apoptosis-inducing activity of a mitochondrially targeted temperature-sensitive p53 in stable transfectants of SaOS-2 cells. In radioprotection assays, which rely on p53, vanadate completely protected mice from a sublethal dose of 8 Gy and partially from a lethal dose of 12 Gy. Together, our findings indicated that vanadate effectively suppresses p53-mediated apoptosis by both transcription-dependent and transcription-independent pathways, and suggested that both pathways must be inhibited to completely block p53-mediated apoptosis.

Cerium vanadate nanorod arrays from ionic chelator-mediated self-assembly

Abstract: Historically, there has been a constant effort to fabricate assembled regular superstructures from individual inorganic building blocks by “bottom-up” approaches. Generally, monodisperse building blocks, modification of the colloid surface with long-tail surfactants, stable suspension in organic solvents, and controlled evaporation of solvent molecules have been considered as key factors for preparation of such superstructures. In the last five years, alignment of nonspherical nanoparticles, especially one-dimensional nanoparticles, with intensified anisotropy has attracted vast attention, because such nanostructures allow investigation of the influence of size and dimensionality along with the collective optical and electronic properties of the particles, and they meet the needs of many practical applications. However, the inert and insulating nature of surface organic ligands results in very poor interparticle coupling. Construction of novel nanocrystal (NC) assemblies with active intermediate reagents remains a challenge. Very recently, a breakthrough was made by Kovalenko et al., who demonstrated that molecular metal chalcogenide complexes (MCCs) could stabilize colloids while preserving the ability of monodisperse NCs to form periodic structures (superlattices). Herein, we report 1D CeVO4 nanorod (NR) arrays in very salty aqueous solution from self-assembly under direction of an ionic multidentate ligand “glue”, EDTA (ethylenediaminetetraacetic acid). Lanthanide orthovanadates are currently attracting broad attention owing to their prospective applications in many fields, for example as catalysts, laser host materials, and phosphors. The ability to assemble lanthanide orthovanadate nanorod arrays should enable new types of applications with collective chemical and physical properties. Moreover, formation of such superstructures not only provides the opportunity to study the electronic communication between the NCs, but more importantly, it provides a new model for 1D nanostructure assembly and might lead to new directions for superstructure construction. Assembly of CeVO4 nanorods accompanied their hydrothermal synthesis from cerium nitrate and ammonium metavanadate with assistance from EDTA. After hydrothermal treatment at 180 8C for 6 h, brown aggregates formed at the bottom of the autoclaves. As-formed products had a sheet-like appearance in the low-magnification SEM image (Figure 1a). A top view of the sheets demonstrates the striking long-range order of the assembly with a tetragonal close-packed arrangement of CeVO4 NRs (Figure 1b, only the square rod ends are visible). Figure 1c gives the side view of the CeVO4 NR arrays with several layers, thus indicating that the NRs (l 70 nm, d 10 nm) stand upright in the layer. The NRs are fairly uniform in each assembly and stack together in an ordered phase, forming a smectic-like structured superlattice, as schematically shown in the inset of Figure 1d. Note that these assemblies often range over several micrometers (Figure 1a), while only a small section of them is shown. These side-by-side, assembled NRs are oriented approximately perpendicular to the layer, leading to a unusual X-ray diffraction (XRD) pattern of CeVO4 superstructures (Figure 1d) compared to the standard zircon-type pattern (space group I41/amd, JCPDS 79-1065). Peaks related to the c axis, including (112), (103), (204), and (004), were significantly strengthened, but (h,k,0) peaks, including (200) and (220), were obviously weakened. These results implied that the h001i crystal axis is perpendicular to the sheet plane of the NR array. In contrast, as the arrays were broken into individual rods and small bundles under repeated cycles of washing, sonication, and centrifugation (see the Supporting Information, Figure S1), the peak intensities become consistent with those in the JCPDS card. TEM and high-resolution TEM (HRTEM) gave further insight into the crystal structure and smectic-like assembly of CeVO4 NRs (Figure 1e–g). The multilayer arrays were exfoliated into single-layer sheets by dilution and weak sonication, which implied a weak interlayer interaction (see the Supporting Information, Figure S2). The low-magnification TEM image (Figure 1e) and its fast Fourier transform (inset) demonstrated the long-range tetragonal packing order. The clear lattice fringes in the HRTEM images that were taken parallel and perpendicular to the c axis of individual NRs in the array (Figure 1 f,g) unambiguously demonstrated the exclusive growth of NRs along the c axis, as indicated by the arrow in Figure 1g and in the model shown in the inset. At the same time, HRTEM also revealed the existence of amorphous matter among the CeVO4 NRs. Each rod in the array was separated by a regular spacing of about 3 nm (see [*] Dr. J. F. Liu, L. L. Wang, Prof. X. M. Sun State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology Beijing 100029 (China) E-mail: sunxm@mail.buct.edu.cn

Use of hydrotalcites for the removal of toxic anions from aqueous solutions

Abstract: The removal of toxic anions has been achieved using hydrotalcite via two methods: (1) coprecipitation and (2) thermal activation. Hydrotalcite formed via the coprecipitation method, using solutions containing arsenate and vanadate up to pH 10, are able to remove more than 95% of the toxic anions (0.2 M) from solution. The removal of toxic anions in solutions with a pH of >10 reduces the removal uptake percentage to 75%. Raman spectroscopy observed multiple A1 stretching modes of V−O and As−O at 930 and 810 cm−1, assigned to vanadate and arsenate, respectively. Analysis of the intensity and position of the A1 stretching modes helped to identify the vanadate and arsenate specie intercalated into the hydrotalcite structure. It has been determined that 3:1 hydrotalcite structure predominantly intercalate anions into the interlayer region, while the 2:1 and 4:1 hydrotalcite structures shows a large portion of anions being removed from solution by adsorption processes. Treatment of carbonate solutions (0.2 M) containing arsenate and vanadate (0.2 M) three times with thermally activated hydrotalcite has been shown to remove 76% and 81% of the toxic anions, respectively. Thermally activated hydrotalcite with a Mg:Al ratio of 2:1, 3:1, and 4:1 have all been shown to remove 95% of arsenate and vanadate (25 ppm). At increased concentrations of arsenate and vanadate, the removal uptake percentage decreased significantly, except for the 4:1 thermally activated hydrotalcite. Thermally activated Bayer hydrotalcite has also been shown to be highly effective in the removal of arsenate and vanadate. The thermal activation of the solid residue component (red mud) removes 30% of anions from solution (100 ppm of both anions), while seawater-neutralized red mud removes 70%. The formation of hydrotalcite during the seawater neutralization process removes anions via two mechanisms, rather than one observed for thermally activated red mud.

Room temperature synthesis and high temperature frictional study of silver vanadate nanorods.

Abstract: We report the room temperature (RT) synthesis of silver vanadate nanorods (consisting of mainly beta-AgV O(3)) by a simple wet chemical route and their frictional study at high temperatures (HT). The sudden mixing of ammonium vanadate with silver nitrate solution under constant magnetic stirring resulted in a pale yellow coloured precipitate. Structural/microstructural characterization of the precipitate through x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the high yield and homogeneous formation of silver vanadate nanorods. The length of the nanorods was 20-40 microm and the thickness 100-600 nm. The pH variation with respect to time was thoroughly studied to understand the formation mechanism of the silver vanadate nanorods. This synthesis process neither demands HT, surfactants nor long reaction time. The silver vanadate nanomaterial showed good lubrication behaviour at HT (700 degrees C) and the friction coefficient was between 0.2 and 0.3. HT-XRD revealed that AgV O(3) completely transformed into silver vanadium oxide (Ag(2)V(4)O(11)) and silver with an increase in temperature from RT to 700 degrees C.

High-temperature hot corrosion behavior of gadolinium zirconate by vanadium pentoxide and sodium sulfate in air

Abstract: Gadolinium zirconate (Gd 2 Zr 2 O 7 ) prepared by solid state reaction exhibited a defect fluorite-type structure. Reactions between Gd 2 Zr 2 O 7 ceramic and vanadium pentoxide (V 2 O 5 ), sodium sulfate (Na 2 SO 4 ), and V 2 O 5 + Na 2 SO 4 mixture were investigated from 700 to 1000 °C in air using an X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). V 2 O 5 reacts with Gd 2 Zr 2 O 7 to form gadolinium vanadate (GdVO 4 ) and monoclinic zirconia ( m -ZrO 2 ) at 900 and 1000 °C in air. However, no chemical reaction product between Na 2 SO 4 and Gd 2 Zr 2 O 7 is found at 900 and 1000 °C in air. V 2 O 5 reacts with equal molar Na 2 SO 4 to form sodium vanadate (NaVO 3 ) at 610 °C. In the temperature range of 700–1000 °C, Na 2 SO 4 + V 2 O 5 mixture reacts with Gd 2 Zr 2 O 7 in air to form the final reaction products of GdVO 4 and m -ZrO 2 .

Adsorption of vanadate(V) on Fe(III)/Cr(III) hydroxide waste.

Abstract: Adsorption of vanadate(V) from aqueous solution onto industrial solid ‘waste’ Fe(III)/Cr(III) hydroxide was investigated. HCl treated Fe(III)/Cr(III) hydroxide was found to be more efficient for the removal of vanadate(V) compared to untreated adsorbent. The adsorption follows second-order kinetics. Langmuir and Freundlich isotherms have been studied. The Langmuir adsorption capacity (Q 0) of the treated and untreated adsorbents was found to be 11.43 and 4.67 mg g−1, respectively. Thermodynamic parameters showed that the adsorption process was spontaneous and endothermic in the temperature range 32–60°C. Maximum adsorption was found at system pH 4.0. The adsorption mechanism was predominantly ion exchange. Effect of other anions such as phosphate, selenite, molybdate, nitrate, chloride, and sulfate on adsorption of vanadium has been examined.

Synthesis and Characterization of Electrospun Poly(ethylene oxide)/Europium-Doped Yttrium Orthovanadate (PEO/YVO4:Eu3+) Hybrid Nanofibers

Abstract: Europium-doped yttrium orthovanadate/polyethylene oxide nanofibers were fabricated by firstly, synthesizing crystalline YVO4:Eu3+ nanoparticles using an aqueous precipitation method followed by electrospinning of PEO/YVO4:Eu3+ polymer composites. X-ray diffraction patterns showed that the nanoparticles exhibited well-defined peaks that were indexed as the tetragonal phase of YVO4. No additional peaks of other phases were observed indicating that Eu3+ ions were effectively built into the YVO4 host lattice. The photoluminescence spectra for the nanofibers showed peaks at 593, 615, 650, and 698 nm which was ascribed to the 5D0− 7F1, 5D0− 7F2, 5D0− 7F3 and 5D0− 7F4 transitions of Eu3+. Due to an efficient energy transfer from vanadate groups to Eu3+, the composite nanofibers showed a strong red emission under ultraviolet excitation characteristic of the red luminescence of the europium ion. The results demonstrate that this synthetic approach could prove to be viable for the fabrication of rare earth/polymer ...

Post-fusion treatment with MG132 increases transcription factor expression in somatic cell nuclear transfer embryos in pigs.

Abstract: The objective of this study was to examine the effect of post-fusion treatment of somatic cell nuclear transfer (SCNT) oocytes with the proteasomal inhibitor MG132 on maturation promoting factor (MPF) activity, nuclear remodeling, embryonic development, and gene expression of cloned pig embryos. Immediately after electrofusion, SCNT oocytes were treated with MG132 and/or caffeine for 2 hr, vanadate for 0.5 hr, or vanadate for 0.5 hr followed by MG132 for 1.5 hr. Of the MG132 concentrations tested (0-5 microM), the 1 microM concentration showed a higher rate of blastocyst formation (25.9%) than 0 (14.2%), 0.5 (16.9%), and 5 microM (16.9%). Post-fusion treatment with MG132, caffeine, and both MG132 and caffeine improved blastocyst formation (22.1%, 21.4%, and 24.4%, respectively), whereas vanadate treatment inhibited blastocyst formation (6.5%) compared to the control (11.1%). When examined 2 hr after fusion and 1 hr after activation, MPF activity remained at a higher (P < 0.05) level in SCNT oocytes that were treated post-fusion with caffeine and/or MG132, but it was decreased by vanadate. The rate of oocytes showing premature chromosome condensation was not altered by MG132 but was decreased by vanadate treatment. In addition, formation of single pronuclei was increased by MG132 compared to control and vanadate treatment. MG132-treated embryos showed increased expression of POU5F1, DPPA2, DPPA3, DPPA5, and NDP52l1 genes compared to control embryos. Our results demonstrate that post-fusion treatment of SCNT oocytes with MG132 prevents MPF degradation and increases expression of transcription factors in SCNT embryos, which are necessary for normal development of SCNT embryos.

Four nodal self-catenated [{Ni8(Bpy)16}V24O68]·8.5(H2O), combining three dimensional metal–organic and inorganic frameworks

Abstract: The chiral three dimensional crystal structure of [{Ni8(Bpy)16}V24O68]·8.5(H2O) is the first example of a hybrid vanadate combining a three dimensional metal–organic subnet with a three dimensional inorganic framework. The metal–organic framework consists of 3D + 2D polycatenation of a 3D “cds” like net and two 2D “sql” layers. The vanadium oxide subunit is a complex chain constructed from V5O15 cycles linked through a single tetrahedron. The vanadate chains are located in the channels of the metal–organic framework, and corner linked to the nickel metal centres giving rise to an unprecedented four nodal self-catenated framework. Moreover, as far as we as concerned, this is the first vanadate in which the V5O15 cycles has been isolated in the solid state. The crystallization water molecules are partially encapsulated between the organic ligands and the inorganic framework. The loss of crystallization water molecules gives rise to a contraction of the 0.6% of the unit cell volume. The IR spectrum shows the characteristic bands of the vanadium oxide subunit, and the bpy ligand. The BET measurement gives rise to a type III profile, (3.7 cm2 g−1), suggesting weak adsorbate-adsorbent interactions. The thermal evolution of the magnetic susceptibility is attributed to the zero-field splitting for eight non interacting Ni(II) cations.

Optical properties of Nd-doped rare-earth vanadates

Abstract: Rare-earth orthovanadates are being used as substitutes for traditional solid-state laser hosts, such as YAG. While the most common of these is yttrium orthovanadate, other rare-earth vanadates, such as lutetium vanadate and gadolinium vanadate, are being used for their special properties in certain applications. We report new measurements of the refractive indices and thermo-optic coefficients of these materials, which will aid in the design of laser cavities and other nonlinear optical elements.

Molten salt synthesis and structural characterization of novel salt-inclusion vanadium bronze Cs5FeV5O13Cl6.

Abstract: Single crystals of a new reduced vanadate phase, Cs5FeV5O13Cl6, have been grown from the reaction of metal oxides V2O5 and Fe2O3 in the presence of a metal reducing agent in a eutectic CsCl/NaCl flux. This compound adopts a tetragonal structure (P4/nmm, a = 10.943(3) A, c = 10.535(4) A, Z = 2) that consists of reduced vanadate layers separated by ionic layers comprised of [FeCl6]3− anions and Cs+ cations. There are two distinct vanadium sites in the structure of this compound; V4+ is in square pyramidal configuration, and V5+ has a tetrahedral coordination environment. The 51V NMR Knight shift and the magnetic susceptibility data indicate the delocalization of the unpaired electron of vanadium. Ferrimagnetic ordering is observed at 5 K.

Transition-metal vanadate or mixed transition-metal / rare earth vanadate based catalyst composition for selective catalytic reduction of exhaust gases

Abstract: A catalyst composition represented by the general formula XVO4/S wherein XVO4 stands for TransitionMetal-Vanadate, or a mixed TransitionMetal-/RareEarth-Vanadate, and S is a support comprising TiO2.

A functional calcium-transporting ATPase encoded by chlorella viruses

Abstract: Calcium-transporting ATPases (Ca2+ pumps) are major players in maintaining calcium homeostasis in the cell and have been detected in all cellular organisms. Here, we report the identification of two putative Ca2+ pumps, M535L and C785L, encoded by chlorella viruses MT325 and AR158, respectively, and the functional characterization of M535L. Phylogenetic and sequence analyses place the viral proteins in group IIB of P-type ATPases even though they lack a typical feature of this class, a calmodulin-binding domain. A Ca2+ pump gene is present in 45 of 47 viruses tested and is transcribed during virus infection. Complementation analysis of the triple yeast mutant K616 confirmed that M535L transports calcium ions and, unusually for group IIB pumps, also manganese ions. In vitro assays show basal ATPase activity. This activity is inhibited by vanadate, but, unlike that of other Ca2+ pumps, is not significantly stimulated by either calcium or manganese. The enzyme forms a 32P-phosphorylated intermediate, which is inhibited by vanadate and not stimulated by the transported substrate Ca2+, thus confirming the peculiar properties of this viral pump. To our knowledge this is the first report of a functional P-type Ca2+-transporting ATPase encoded by a virus.

Controllable solvo-hydrothermal electrodeposition of lithium vanadate uniform carnation-like nanostructure and their electrochemical performance

Abstract: In this paper, we successfully developed a novel method to synthesize uniform carnation-like lithium vanadate nanostructures by combining electrochemical deposition and solvo-hydrothermal method. The samples were characterized by field emission scanning electron microscopy, power X-ray diffraction, and thermogravimetric analysis. The results show that the LiV3O8·H2O carnation-like nanostructure is 2–3 μm in diameter and assembled from nanosheets with thickness of 10–20 nm. Based on a series of experiments, we proposed a possible growth mechanism, in which the supersaturation derived from electric field and high conductivity under solvo-hydrothermal conditions due to the successive growth of lithium vanadate. In our work, we have discussed three different solvo-hydrothermal systems. It is proved that the morphology of coating materials could be conveniently controlled by selecting alcohols with different chain of alkyl. Compared with short-chain alcohol, CH3–(CH2)6–CH2–OH was beneficial to promote the oriented growth of nanosheets. Electrochemical performances of lithium vanadate cathode materials were characterized by galvanostatic charge–discharge, and LiV3O8 synthesized in n-octanol aqueous solution exhibits the highest capacity of 357 mAh g−1 and best cycle stability. Furthermore, the influence of solvo-hydrothermal conditions on the morphology and electrochemical performance of products has also been studied.

Oxidative dehydrogenation of butane over substoichiometric magnesium vanadate catalysts prepared by citrate route

Abstract: Substoichiometric magnesium vanadate catalysts, (Mg–V i with i = 1, 2, and 3) with different V/Mg atomic ratios and stoichiometric (Mg 3 V 2 O 8 , Mg 2 V 2 O 7 and MgV 2 O 6 ), were prepared by citric acid technique. Characterization showed that substoichiometric samples correspond to well-dispersed VO 4 units in the MgO matrix. Moreover, taking into account the Raman data, the coexistence of ortho, pyro and meta vanadate phases cannot be discarded. The Mg 3 V 2 O 8 sample was more active for the oxidative dehydrogenation of n -butane, but less selective to C 4 alkenes than the Mg 2 V 2 O 7 sample. Stoichiometric samples produce mainly 1-butene, whereas for substoichiometric samples butadiene was the major reaction product for reaction temperatures higher than 748 K. The easily reducible VO 4 species, and eventually the coexistence of different vanadates phases, appear to be responsible for the catalytic behaviour displayed by the substoichiometric catalysts prepared by citrate technique.

Crystallization of Calcium Vanadate Solids from Solution: A Metathetic Route

Abstract: Microwave mediated metathetic solid state reaction between NaVO3 or NH4VO3 and CaCl2 followed by dissolution in aqueous solution resulted in the crystallization of four calcium vanadate hydrates: CaV2O6·4H2O (1), CaV2O6·4.25H2O (2), CaV2O6·5H2O (3), and (NH4)2[{Ca(H2O)7}2V10O28]·2H2O (4). Single crystal X-ray diffraction analysis of the three pseudopolymorphs 1−3 revealed that the crystal packing is dominated by the presence of ladder-type {V2O6} chains made of edge-shared VO5 square pyramids interconnected via calcium hydrate chains. The way the system accomplishes the variation in water of hydration through interesting H-bonding interactions between calcium hydrates and the vanadate chains is an example of smart crystal engineering; 3 shows the occurrence of an unusual tetrameric H-bonded water cluster. In contrast, 4 is a decavanadate cluster based solid. The paper proposes a retrosynthetic approach to understand the crystal packing of the vanadate solids through intuitive mechanisms that provide insig...